• On the ground, Special Forces soldiers and CIA operatives already are inside Iraq, working with Iraqis who oppose Saddam Hussein, preparing airstrips and communications facilities, and taking note of potential targets for air attack.

• Iraq, too, is on the move, taking steps that include dispersing its forces to limit the effects of an expected initial air attack.

More than anything, both sides are engaged in the behind-the-scenes efforts that can be crucial to military success: positioning troops, securing supply lines, scouting behind enemy lines, and probing the strength of a foe's defenses.

Even as a diplomatic impasse on Iraq continues at the United Nations, these operations represent the early phase of military efforts that could shape how any war plays out.

The first phase of war also seems to be raising the curtain on a new US approach to defending itself around the world: preemptive attacks instead of just holding in check the source of a threat to national security.

There's no doubt that the US - alone if it had to - could subdue Iraq in fairly short order. With nearly 150,000 troops and five aircraft carrier battle groups in the region, plus heavy bombers within easy flying range, the US is demonstrating its undoubted position as the most militarily powerful nation in history.

This is saber rattling on a very large scale, designed to demoralize Iraqi forces and compel Hussein to realize that he cannot survive with his weaponry - and perhaps his regime - intact.

Meanwhile, the maneuvering at the United Nations is likely to have the effect of changing the nature of any conflict in Iraq. Officials say it now looks likely that any full-blown military action won't happen until later in March or perhaps even April, when temperatures will have begun soaring, making combat much harder for US soldiers.

One main reason for the delay: Saddam Hussein's "rope-a-dope" diplomatic strategy - appearing to be more forthcoming with UN inspectors while continuing to resist real openness about his weapons of mass destruction - plays into the hands of other countries looking for ways to slow (if not prevent) any US move to war. This in itself is a form of warfare - finding a way to affect the timing to one's advantage.

With the UN drama continuing, Iraq is scattering its military units to lessen damage by US and allied bombers, positioning elite units in and around Baghdad, and equipping those forces with protective gear in case chemical weapons are used in a last-ditch fight.

US officials also see evidence that Mr. Hussein is preparing to use scorched-earth tactics - destroying his own infrastructure and oil facilities - to impede attackers while creating a humanitarian crisis that could be blamed on the US and its allies.

The US, for its part, is using airborne leaflets and broadcasts to fight a psychological war that is well under way - warning Iraqi forces against the use of chemical or biological weapons lest they be prosecuted as war criminals, assuring civilians that they will not be targeted.

Since Hussein reportedly has issued hundreds of thousands of rifles and grenade launchers to civilians, this US war-propaganda effort could make a big difference in how any shooting war is conducted - particularly if it involves very difficult urban fighting, as Iraq's military officers now are planning.

Whether or not there is any direct connection between the most important faces on US "wanted" posters these days - Hussein and Al Qaeda leader Osama bin Laden - the fact that both present a highly threatening aspect to the US and to many individual Americans is an important element in Iraq's psychological warfare. Those antiaircraft missiles poised next to the Washington Monument, together with Bin Laden's belligerent tauntings broadcast from some secret hideout, are a stark symbol that the broader "war on terrorism" - now a year and a half on - is far from over. Here, the concern for US officials is that all of this uncertainty and anxiety will lead to flagging public support for war in Iraq.

Another concern is that further delays could cause wear and tear on troops cocked and ready in the Kuwaiti desert and aboard ship, leading to a loss of military momentum.

It may be something that America will have to get used to. The Bush administration's new National Security Strategy includes an important shift in doctrine from deterrence and containment of potential enemies to an emphasis on preemptive strikes against nations or terrorist groups that threaten the US.

This revised strategic posture has brought a new phrase into the political-military lexicon: "perpetual war."